It is a general demand to reduce the power consumption of wireless devices such as UEs or mobile user terminals in wireless communications. Reduced power consumption evidently leads to battery savings, which is an important feature of wireless devices.
Discontinuous Reception, DRX, is a mechanism to conserve battery power in wireless devices and UEs. A UE is then normally configured for DRX operation with a DRX cycle having a DRX ON period in which the UE is in a DRX awake state and ready for reception and a DRX OFF period in which the UE is in a DRX sleep state, as illustrated in FIG. 1. During the DRX OFF period, which is sometimes referred to as the inactivity period, the UE turns its receiver off and enters power saving mode, or sleep state. The length of the DRX ON period combined with the length of the DRX OFF period determines the length of a DRX cycle, which may be periodically repeated. Normally, the network side decides the DRX timing so that the network transmissions can be synchronized with the UE wake-up periods.
Various attempts have been made to develop and improve the design and use of the DRX mechanism.
For example, two types of DRX cycles have been introduced; a long DRX cycle and a short DRX cycle. If no data is received during a short DRX cycle, the UE may switch to a long DRX cycle, which is much more power efficient.
In reference [1] it is proposed to only turn on the UE transceiver for a subset of DRX cycles, e.g. based on the quality of the radio environment.
In reference [2] it is proposed to adapt the length of the DRX cycle based on the available battery power of the mobile device.
In reference [3] it is proposed to delay transmission of a scheduling request based on the DRX time cycle to prevent repeated interruption of the DRX cycle.
In reference [4] it is proposed to schedule the transmission time of uplink frames to occur when the device has powered up so that it can receive a downlink frame.
There is still a general demand for improvements with regard to the design and use of the DRX mechanism in wireless communication networks.